Portable public safety radios are utilized in a variety of environmental and hazardous conditions, and battery packs are typically used to power such radios. Under certain environmental conditions there exists the possibility of a spark being generated when the battery pack is removed or replaced from the radio. Accidental occurrences of short circuits or soft shorts of external battery contacts may be sufficient to create hot spots with the potential to cause sparking problems in the field. It is imperative to avoid any sparking between the device and the battery that might result in an explosion and/or a fire.
Product safety directives have been established under various agencies and standards, such as Factory Mutual (FM) and ATmosphere EXplosible (ATEX) and IECEx to address product safety. Devices operating under these directives or standards are also referred to as intrinsically safe devices.
FIG. 1 shows a prior art shows a partial cut-away view of an intrinsically safe battery pack assembly 100. The prior art battery pack 100 is shown in a cross sectional side view 102, a first perspective view 104, and a second perspective view 106. In side cross sectional side view 102, a plurality of charging and radio interface components 108 are shown disposed upon a printed circuit board (PCB) 110. A pair of spacers 112 are disposed beneath the PCB 110 and coupled to a PCB insulator 114. Beneath the PCB insulator 114 are a plurality of battery cells 116, shown in two stacks. The cell stacks may or may not be staggered. Additional spacers 118 are situated between pairs of vertically stacked cells. A flex insulator 120 covers the last pair of battery cells 116.
Perspective view 104 shows the flex insulator 120 as well as various charging and radio contacts 122. In this view, it can be seen that additional components 124 are located on an opposing side of the PCB 110. The PCB 110 thus extends outward of the cell stacks. In order to accommodate components 124, the cells 116 must be staggered (as shown in view 106), increasing the overall size of the battery pack 100. Additionally, in order to interconnect the PCB components 108, 124 to the charging and radio contacts 122 requires the use of a connector 124 mounted to the PCB. The connector 124 is covered by a portion of the flex 120. Hence, in the case of intrinsically safe battery packs for public safety devices, the battery packs tend to be large and bulky in order to accommodate all of the layered elements and components needed to meet both the power and safety requirements.
When developing an intrinsically safe electronic device for today's portable communication device market, a designer must provide a safe device while addressing the challenges of parts count, board space and ease of manufacturability. Particularly in the case of battery packs for public safety radios, the ability to decrease the overall size, weight, and cost of the battery pack would be highly advantageous.
Accordingly, it would be highly desirable to have an improved battery pack that ensures product safety using few components, taking up little board space and facilitating manufacturing.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.